(i) Field of the Invention
The present invention relates to a method of sequentially spraying a cryogenic liquid, in particular liquid nitrogen.
The invention applies more particularly to the cooling, crusting and freezing of individual food products on their production line. In applications of this type, nozzles which are sequentially fed with liquid nitrogen spray liquid nitrogen onto each food product which is being conveyed.
(ii) Description of Related Art
Optimization of the cooling heat transferred between the jets of sprayed liquid nitrogen and the products to be cooled leads to the choice of drop sizes of between about 10 and 30 microns for the sprayed nitrogen. This dimensional constraint on the drops leads to a constraint on the pressure of the liquid nitrogen feeding the spray nozzles, which must also lie within a certain range.
This pressure constraint limits the reduction in the temperature of the liquid nitrogen feeding the spray nozzles. However, this reduction may itself lead to an increase in the cooling capacity of the liquid-nitrogen spray jets which are produced.